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SALICYLIC ACID                            191

the sodiLiiT-^ phericite by means of a bent tube fixed through the
tubulus of t*10 retort» anc^ terminating just above the substance.
The tem~pGrnt"uie °* ^1C 01^"^at-n 's gradually raised from 140° to
180__loo0?    whilst fresh surfaces  are  exposed  by  occasionally
stirrinc*- vv/itl* a glass rod inserted for a moment through the
tubulus A-t the end of four hours the temperature is raised to 190
—200° foir zxtiother hour, and the process stopped. During the
heatinc^- %\. considerable quantity of phenol distils, and solidifies in
the iiecrlc of l-nc retort, whilst the contents become dark coloured.
The rn^iss is shaken out into a basin without disturbing the phenol
in the necl£> anc^ the residue dissolved by filling the retort two-
thirds full of water. This is poured into the basin containing
the otHcii" portion, which soon dissolves. The solution is acidi-
fied wit In concentrated hydrochloric acid, which throws down
impure sn.lic.:ylic acid in the form of a dark brown pre-
cipitate. "When cold, the precipitate is filtered at the pump,
and w;Exsl"i<:i<^ with a little cold water. A further quantity
may foo ol:>t*lined by evaporating the filtrate to a small bulk. It
is purified l->y dissolving in water, boiling with a little animal
charcon.1 n.iicl filtering. The filtrate deposits the acid, on cooling,
in needles. Yield about 6 grams.
J.    C0T~Ir>0 Na + CO, = C(!II,O.CO.ONa
Sodium phenyl ourboniUi!.
2. CeI-I0O.CO.ONa
I )isodiuin siilicylulc.
Projf*£??*-/****?*- Colourless needles; in. p. 155—156''; soluble in
ilcohoi n.incl hot water, rex)1 parts water dissolve 0*225 part at
15° ancl 7~<J^5 parts at 100".
Iteu£'jft&?zs'. r. Dissolve a little of the acid in water and add
a drop of" f<e rric chloride. A violet colouration is obtained.
2. Gi" v.ip some of the acid with soda-lime and cover with a
shallow In.yor of the same substance. On heating strongly the
smell of* pliciiiol is perceived.
C0I-I.,<OH)CO.OH + CaO = C6HflOH + CaCO;J.
See ^4.jp2&*??uiiX) p. 297.